There has already been disclosed (WO-A-9535628) the use of a signal which accompanies an MPEG bitstream and which carries information about the bitstream for use in a downstream process, for example, the re-encoding of a decoded MPEG picture. This signal is provided in parallel and is sent along an appropriate side channel to accompany a decompressed signal from a compression decoder to a subsequent encoder.
Where equipment has been specifically designed for use with such a signal, considerable advantage can be gained and many of the problems previously associated with cascaded coding and decoding processes are removed or ameliorated by using in a downstream coding process, key information concerning upstream coding and decoding.
In WO-A-9803017, there are disclosed techniques which extend these advantages, in part or in whole, to arrangements which include equipment not specifically designed for use with such a signal. Specifically, these techniques include embedding the information signal in the video signal so that it can pass transparently through a video pathway.
It is an object of this invention to provide improved apparatus and processes which offer benefits not just in a cascaded recoding operation but primary coding operation.